Thick film resistor assembly for fan controller

Abstract

A power resistor assembly includes an anodizable metal substrate, preferably an aluminum alloy, having an insulating anodized coating on at least one flat side. A resistive or partially conductive ink is screen printed on the anodized coating in a pattern to provide one or more resistors. The ink has a curing temperature below 660° C. which is below the melting point of aluminum. The resistor assembly is a vehicular fan motor controller or an interior dimmer switch. The fan motor controller has resistor ends which are soldered with tin-lead solder.

I claim: 
     
       1. A fan motor controller comprising a resistor assembly having an anodizable metal substrate having a flat portion and an insulating anodized coating bonded directly to the flat portion;   at least two screen printed thick film power resistors of different resistance value bonded to the anodized coating with an adhesion of at least 0.25 kg/0.01 in 2  and having two ends and a capacity of at least three watts, the thick film power resistor comprising a metal and a fused borosilicate glass binder having a curing temperature below the melting point of the substrate and below 660° C.; and   a conductive terminal and a solder bonding the terminal to the resistor ends.   
     
     
       2. The fan motor controller of claim 1 wherein the borosilicate glass is a lead borosilicate glass. 
     
     
       3. The fan motor of claim 1, wherein the metal is copper and the terminal is soldered directly to the resistor ends. 
     
     
       4. The fan motor controller of claim 1 wherein the substrate is of a regular polygonal shape having a plurality of edges including a first edge having the insulating coating wrapped from a top surface of the substrate, around the first edge and onto a bottom surface of the substrate,   a plurality of second edges having the insulating coating on a top surface of the substrate and on the bottom surface of the substrate and a bare metal section exposed on the second edges,     the resistor ends being adjacent the first edge, the terminal being connected with tin-lead solder to the terminal pad on one side of the substrate and bonded to the insulating coating on the opposite side of the substrate.   
     
     
       5. The assembly of claim 1 wherein the metal substrate is selected from the group consisting of aluminum, magnesium and alloys thereof. 
     
     
       6. The assembly of claim 5 wherein the metal substrate consists of aluminum and aluminum alloys and has a melting point in the range of 600°-660° C. 
     
     
       7. The assembly of claim 1 wherein the insulating anodized coating has a dielectric strength of at least about 400 volts/mil and has a thickness of at least 0.25 mils. 
     
     
       8. The assembly of claim 1 wherein the substrate is a flat sheet having a thickness less than about three millimeters. 
     
     
       9. The assembly of claim 8 wherein the thickness is about one millimeter. 
     
     
       10. A fan motor controller comprising a resistor assembly having an anodizable metal substrate comprising a flat sheet being no more than about three millimeters thick and having an insulating anodized coating bonded directly to the flat sheet;   at least one screen printed thick film power resistor bonded to the anodized coating with an adhesion of at least 0.5 kg/0.01 in 2  and having two ends and a capacity of at least three watts, the thick film power resistor comprising copper and a low melting point glass having a softening temperature substantially below 660° C. and below the melting point of the substrate; and   a conductive terminal and a tin-lead solder bonding the terminal to the resistor ends.